JP2019537076A - RGB projector with multiple laser broadband light source and system for dynamically controlling image contrast ratio - Google Patents

Abstract

A high dynamic range projector (HDRP) comprises at least one spatial light modulator having red, green and blue digital light projector (DLP) chips and red, green and blue laser light operative to illuminate each DLP chip. And a central processing unit (CPU) coupled to each of the DLP engine and the RGB laser light system, the CPU comprising an RGB laser at a frame rate based on a desired contrast ratio. Operable to determine an optimal average power for each of the optical systems.

Description

  The present disclosure relates to RGB (red (red), green (green), blue (blue)) projectors with multiple laser light sources. In particular, the present disclosure relates to broadband fiber RGB diode lasers that are individually controlled to contribute to speckle reduction, and further relates to a laser beam transmission system for dynamically controlling the contrast ratio of an image.

  The demand for high quality projection displays continues to grow, both from consumers and the creative industry, who want image quality and maximize the cinematic experience. One of the main efforts of the movie industry is to improve the brightness and contrast of images. Recently, major movie and projector companies have been focusing on laser technology. The use of a laser-type projector provides a high-brightness image with a wide color gamut and high contrast ratio at a low cost of ownership (including a long lifetime) over a projector with a conventional xenon bulb. However, simply improving the brightness of the display can cause dark tones to become moderately gray. As a result, there is a need in the art for a new laser light source, as well as a further spread of image contrast, which is the ratio of the scene's lowest intensity to the scene's highest intensity. That is, as the contrast increases, the image can more accurately represent a real world scene. This need is met, in part, by projection displays that utilize high dynamic range (HDR) techniques.

  Advanced HDR display designs are based on digital light projectors (DLPs) and enable a dynamic range that is said to be over 50,000: 1 and as high as 1,000,000: 1. The DLP projector is based on a DLP chip, a digital micromirror device (DMD) consisting of up to millions of small (less than one-fifth of the width of human hair) mirrors. Each mirror of this chip is independently adjustable and changes its angular position with respect to the light source to form dark or light pixels. However, at this point, the image is grayscale. The DMD is given a color by passing the light beam through a rotating prism before reaching the chip. Each part of the prism carries one color. Initially, only the three primary colors red, blue, and green were supported. In more advanced systems, the prism supports cyan, magenta, and yellow in addition to the three primary colors. Chips can produce up to 16.7 million colors, and a three-chip design DLP projector can deliver up to 35 trillion colors. After the color reaches the DMD, an image is provided on the projection screen via a lens.

  During the playback phase, the video information of the camera is processed by a computer-based processing unit of the HDR projector display. This is typically done by inputting image signals based on various criteria that are initially stored in a camera control unit having an image conversion unit or scaler. The scaler integrates the input image signal as an image signal having a projection format, stores the signal in a video RAM, and then sends the signal to a processing unit. The processing unit uses each transmitted image signal to multiplex the frame rate (for example, 60 frames per second) that matches a predetermined format, the number of divisions of color components, and the number of gradations of the display. The reflection micro element is driven based on the driving.

  In practice, the processing unit is designed to enhance the contrast based on the data transmitted from the camera. Thus, the operation of the unit is based on a specific algorithm that manages the output of the laser-type light source and the selective "on" and "off" positions of the DMD. However, in some known HDR projectors, the laser-type light source does not always operate efficiently, which results in a relatively short life of the light source, high maintenance costs, and other known disadvantages. Therefore, it is desired to optimize the operation of the laser light source of the HDR projector.

  Further, at least some HDR projector operations require that a person, such as a videographer or film maker (video writer), change the output of the laser light source to change the pre-programmed contrast according to the person's vision. No means. Accordingly, it is desirable to provide a HDR display with a contrast improvement method that allows a movie maker to modulate the intensity of a laser-type light source.

FIG. 2 is a schematic diagram of the HDR concept of the present invention including modulation of laser light source output. 1 shows one configuration of an RGB laser light source. 5 shows another configuration of the laser-type light source. 4A-4C illustrate the design and operating principles of the green fiber optic laser system of the present disclosure. FIG. 4 shows a schematic end view of a DMD chip. FIG. 4 shows a schematic diagram of an optical system that includes one or more of the light sources of FIGS. 1-3 that provide power to a plurality of displays.

  The HDR projection display system 50 shown in FIG. 1 is provided with a control channel between each of a red laser light source 52, a green laser light source 54, and a blue laser light source 56, and a control unit 18 of an HDR projector 60. The control unit allows an operator to modulate the output of each light source to change the brightness of the originally generated image according to the on-board algorithm as needed.

  In particular, the display 50 of the present disclosure controls the operation of the laser according to a given video frame (i.e., one of a number of individual still images that make up a complete moving image) and between successive frames. Operable to change. This can be accomplished using a controller 55 that is coupled to the inputs of the laser systems 52, 54, 56 and that each of the laser outputs or in response to an external signal to the controller 55. Change the strength of those combinations. For example, if the contrast ratio meets the requirements of the film maker, the changed intensity is stored in the control processing unit 18 of the HDR projector 60. An HDR projector has at least one light modulator, but can also be configured to have two light modulators, each light modulator having three DLP engines corresponding to the red, green, and blue primary colors, respectively. Including.

  To outline the operation of the HDR display 50, two or all three laser systems emit each output beam, which are then combined with white light, homogenized with a rectangular integrator rod, and combined. And outputs a homogenized beam. The homogenized beam then enters the Philips prism and is split into red, green and blue components. These components illuminate each DLP engine, and each engine forms an image of the corresponding color in the pixel array. Further, portions of each incident light component reflected from each DLP engine may be recombined for further contrast enhancement and / or projected directly to screen 30 via lens 40.

In some RGB display, ^{two 16} stage or 65,636 steps or more levels may be present for each primary color. Typically, a frame with a uniform white or black color will rarely occur as compared to a frame containing multiple color images. The contrast of the color image is determined by an algorithm operation controller 18 that mixes two or three primary colors of light and positions each DMD in an on position, an off position, and a position therebetween. Need to change.

  A given frame or image typically has the brightest and darkest points determined by known sensor systems. As is known, light leaks onto the screen even when the DMD is in the "off" position and does not reflect light. No one is really surprised to see traces of light color due to light leakage on a screen that should be black. However, the concept of the present invention is to reduce the intensity of the output of one or more lasers selectively, depending on a given frame, or to completely turn off unnecessary laser systems, for example. Signs of unwanted light on the frame can be significantly reduced. All necessary information regarding the intensity of each laser system for a given frame is stored in the controller 18 and the frame so edited is placed on the screen 30 using the feedback loops R62, G64, B66 respectively. Used to automatically reduce / increase the output intensity of the light source at the point in time when the image is taken.

  The laser systems 52, 54, 56 operate in a pulsed manner and are selectively controllable to output pulses in synchronization with displacing the mirror to an "on" or "off" position. As described in detail below, the red fiber system 52 and the green fiber system 54 each operate at a pulse repetition rate that significantly exceeds the frame rate. Typically, the duration of each frame is approximately 15 μs, which is substantially greater than the pulse repetition rate. The difference in rate between the frame and the pulse repetition contributes to enhanced dynamic contrast ratio control, as described below.

  The above points can be better understood with reference to FIG. 5, which shows a DLP chip 84. For example, assume that only some of the DMDs 86 located at the bottom of chip 84 are required to be in the "on" position. One or more pulsed light sources 52-56 of the fiber system such that the fiber laser system outputs one or more pulses in synchronization with displacing the required DMD to the "on" position in accordance with a command from controller 18. Can be operated. Such a synchronized operation of the DMD and the pulsed light source of the fiber system can be easily established by controlling the duty cycle of the pulsed light source or each fiber system. In addition to the pre-programmed synchronization, the operator can manually rewrite the program using the external input 55 to change the predetermined contrast ratio. The modulation of the output of the fiber laser system is controlled so that the frequency conversion efficiency of the light of the green, red and blue systems is not affected.

  Each frame always has the brightest point, unless it is required that it be completely black and completely dark, but that point will typically be the maximum possible corresponding to having all DMDs on the chip in the on position. Lower than the brightness. This allows to optimize the laser operation for a given frame. The data received by the controller 18 of the projector 60 from the cameras includes the number of DMDs in the "on" position and the DMDs in the off position of each DLP to provide the desired contrast for each frame. However, the output power of the laser light source is often maintained at a constant level or above a minimum that can provide the required contrast ratio. The operation of such a laser can adversely affect its functionality and maintenance costs.

  To minimize the above drawbacks, the controller 18 is configured to obtain the desired contrast ratio between the lightest and darkest pixels for a given frame as determined by means 94 known to those skilled in the art. All or optional laser systems 52-56 are operable to determine a minimum average power. Once the minimum average power for the calculated ratio has been determined, the controller 18 can operate to controllably reduce the average output power of all or selective laser systems at a frame rate. . The structures and methods of the present disclosure help lower the operating temperature of laser light sources and reduce power consumption, all of which translate into longer life and lower maintenance costs.

The structure of FIG. 1 also has an external input 55 that can be accessed by a movie maker. It may be desirable to override the pre-programmed or newly determined output of the laser system. The film maker can use the input 55 to manually modulate the output intensity according to his or her concept to obtain the desired ratio, and the desired ratio can be stored in the CPU 18. .

  Preferably, the light sources of the present disclosure include a red fiber laser system 52, a green fiber laser system 54, and a blue fiber laser system 56. However, the scope of the present disclosure is not limited to fiber systems only, and may include combinations of diodes, fibers, and other laser configurations. For example, the red laser system 52 and the green laser system 54 can be fiber laser systems, while the blue laser system 56 is preferably a diode laser type. The fiber laser system is configured to output pulsed light, which is directed to the projector 60 via a train of transmission fibers. Each of the laser systems 52-56 may have one or more laser modules, and each laser module includes only one fiber oscillator, but typically includes a master oscillator power fiber amplifier (MOPFA). Fiber amplifier) design.

Figure 2 shows a configuration of a light source of the present disclosure, each of the fiber laser system 52 to 56 which is selected includes a plurality of modules ₇₀ 1 to 70 _n each having a transmission fiber ₇₂ 1 to 72 _n. The modules that emit uniform color light are controlled by a controller 18 that reduces the output intensity of some or all of the modules when needed in a given frame, or Operable to shut down completely.

FIG. 3 illustrates another configuration of the light source of the present disclosure, wherein each of the selected fiber laser systems 52-56 includes a single module 74. However, the output from the module 74 can be selectively induced in the projector 72 via a plurality of transmission fibers ₇₂ 1 to 72 _n. The distribution of light around the transmission fiber 72 can be realized using a scanner 76 operated by the controller 18 which controls the operation of the scanner to the selected on / off position and location of the DMD. Synchronize.

Each of the laser light source configurations of the present disclosure shown in FIGS. 2 and 3 has a fiber coupler having an output fiber 82 that directs collective light from a plurality of fibers 72 ₁ -72 _n to projector 60 of FIG. 82 may be additionally provided. Like the configuration of FIGS. 2 and 3 when no coupler, configured with coupler, selective transmission fiber 72 ₁ before the light of the same color are combined into a single output fiber 82 operates to be guided along the to 72 _n.

  Returning to FIG. 5 above, in either of the configurations of FIGS. 2 and 3, when modified to have no coupler 80, the output end of each transmission fiber 72 that directs the same color will have a corresponding DMD chip 84 And can be juxtaposed directly. Utilizing the flexibility of the control circuit of FIG. 1, light of the same color may be guided only by the fiber 72 facing the desired segment of the chip 84. This feature can be used in addition to the synchronous operation of the DMD and the light source.

  Fiber lasers are known to be of long life, high wall plug efficiency and ultra-high spatial brightness, transmitting power in a very collimated beam from a very small spot. These unique optical properties make it possible to achieve performance that is important for movies and, consequently, for new types of laser lighting: the ability to input an almost unlimited amount of RGB light into a digital projector and the efficient and flexible optical fiber. To achieve the ability to transmit visible light in kilowatts. Another distinguishing feature of fiber lasers is the inherently narrow band, which contributes to the perception of fully saturated colors.

  Unfortunately, the random incidence of narrowband light on rough surfaces (such as the projection screen 30) also introduces unacceptable image artifacts known as "speckle". The speckle visual effect impairs the aesthetic quality of the image and also results in reduced image resolution. As a result, for high resolution display systems, it is generally important to eliminate speckle. Ideally, the spectral bandwidth of the light source of the projection display is on the order of a few nanometers, has a minimum value of 4 nm, and is desirably broad on the order of 20 nm. Such light sources are considered to be quasi-monochromatic, that is, have a sufficiently wide band for canceling speckle, but a sufficiently narrow band for color purity. The light source of the present disclosure is configured to output broad emission radiation, as described below, to minimize speckle effects.

  As is known, the frame rate is at most 120 frames per second. In practice, frame rates are typically below 60 fps or 60 Hz. This is much lower than the frequency at which the laser output can be modulated (typically in the frequency range above KHz). Such a high frequency may even allow the laser light source to be completely shut down between successive frames. This gradually increases the efficiency of the light source, which is a decisive advantage in the highly competitive cinema and display industry.

  Further modifications of the light source include using one high power fiber laser light source that powers multiple HDR displays via beam switch assembly 65, as shown in FIG. This design is particularly suitable for theme parks. The use of multiple displays with the single light source of FIGS. 1-3 can be realized using a beam switch.

  As is known, rare earth metal ions, which are typically used as luminescent ions in a fiber, emit light within a predetermined wavelength range. If the desired wavelength range is outside the range naturally available for a given type of luminescent ion, additional approaches are used. For example, by using a frequency conversion method, each wavelength range of red, green, and blue can be obtained.

FIG. 4A schematically illustrates one modification of a green fiber laser system 52 configured in accordance with the present disclosure. The fiber laser pump 85 preferably has a MOPFA design, outputs pulsed broadband light in the 1 micrometer range, such as 1064 nm typical for ytterbium (Yb) ions, and has a good less than 2, preferably less than 1.1. with the M ² value. Broadband light having a linewidth between 1 nm and 30 nm is incident on a second harmonic generator (SHG), which is a non-critical phase-matched nonlinear crystal 90, such as boric acid. Including lithium (LBO), the crystal is controllably arranged to spend the beam within the crystal. The output of the crystal 90 includes broadband green light centered at a wavelength of approximately 532 nm and having a spectral linewidth λ ₁ -λ _{n of up} to 10-15 nm.

The frequency conversion bandwidth can be induced by creating a constant temperature gradient along substantially the entire length of the crystal 90. The phase matching wavelength of the crystal 90 depends on the crystal temperature. When a constant temperature gradient is imposed within the crystal, the phase matching conditions for different wavelengths defining λ ₁ -λ _n are met at different points along the crystal, giving a wide conversion bandwidth, which is more than sufficient. Suppress speckles.

By providing two thermoelectric coolers (TECs) controlled by the controller 18 of FIG. 1 to maintain the desired temperature gradient regardless of atmospheric conditions, the desired temperature gradient T _n -T ₁ can be maintained. Can be realized. When the temperature _{T 1} is higher than _{T n,} the wavelength to be converted increases in lambda _n from lambda _1.

  The beam from the laser pump may have a bell shape as shown in FIG. 4B. However, the line widths λ1 to λn are slightly smaller than the line width of the flat top beam in FIG. 4C. Therefore, a flat top beam is often preferred. By displacing TECs 92 and 94 along double arrow A using suitable means, the converted wavelength band can be controlled. At present, the crystal 90 can have a maximum length of 5 mm, but longer crystals are also being tested.

  Another configuration of a green fiber laser system is disclosed in WO20150916 by the applicant, which is fully incorporated herein by reference. Also, a red fiber laser light source may have the configuration disclosed in WO20150916, which is also fully incorporated herein by reference.

  Although the present disclosure has been described with reference to the described examples, numerous modifications and / or additions to the embodiments described above will be readily apparent to those skilled in the art without departing from the scope and spirit of the appended claims. It becomes.

18 Control unit 30 Projection screen 40 Lens 50 HDR projection display system 52 Red laser light source 54 Green laser light source 56 Blue laser light source 60 HDR projector 62, 64, 66 Feedback loop

Claims (15)

A high dynamic range projector,
At least one spatial light modulator having red, green and blue digital light projector chips;
A laser light source including red, green and blue pulsed light laser systems operative to illuminate each digital light projector chip;
A central processing unit coupled to each digital light projector chip and each pulsed light laser system, wherein the central processing unit optimizes the average of each pulsed light laser system at a frame rate based on a desired contrast ratio. Operating to determine power, wherein each pulsed optical laser system is operative to output a pulse in synchronization with the selective digital micromirror of the corresponding pulsed optical laser system being displaced to the on position. Dynamic range projector.   2. The sensor system of claim 1, further comprising a sensor system operable to detect a lightest pixel and a darkest pixel in each frame and generate a signal coupled to a central processing unit operable to determine a desired contrast ratio. The high dynamic range projector according to 1.   3. The high dynamic range projector according to claim 1 or 2, further comprising a control channel operable to receive an external input from an image writer and modulate the output of the laser light source to change a desired contrast ratio.   4. A high dynamic range projector according to any one of the preceding claims, wherein at least each of the red and green pulsed light laser systems is configured to have a master oscillator output fiber amplifier.   5. A high dynamic range projector according to any one of the preceding claims, wherein each of the red and green pulsed light laser systems includes a single master oscillator output fiber amplifier module and a plurality of transmission fibers.   6. The method according to any one of the preceding claims, wherein each of the red and green pulsed light laser systems includes a plurality of master oscillator output fiber amplifier modules, each master oscillator output fiber amplifier module being provided with a transmission fiber. High dynamic range projector.   7. The high dynamic range projector according to claim 5, further comprising a fiber coupler coupling the output end of the transmission fiber to a single system output fiber. The green pulsed light laser system
A pump for outputting a pulsed broadband light beam having a bandwidth of 1 nm to 20 nm;
A second harmonic generator receiving the pulsed broadband light beam,
Imposing a temperature gradient within the nonlinear crystal of the second harmonic generator to provide phase matching conditions for a plurality of wavelengths within the bandwidth of the pulsed broadband light beam along substantially the entire length of the nonlinear crystal. A green light beam from the non-linear crystal having a wide conversion bandwidth that is substantially half the bandwidth of the broadband light beam of the pump; 8. A high dynamic range projector according to any one of the preceding claims, wherein the width is sufficient to suppress speckle on the screen.   9. The high dynamic range projector according to claim 8, wherein the broadband light beam from the pump has a bell shape or a flat top shape.   High dynamic range projector according to any of the preceding claims, wherein the green pulsed light laser system is configured as described in WO20150916.   A high dynamic range projector according to any of the preceding claims, wherein the red pulsed light laser system is configured as described in WO20150916.   The high dynamic range projector according to any one of claims 1 to 11, wherein the central processing unit operates to completely stop the laser light source between successive images. A method for dynamically increasing the contrast ratio of the projector according to claim 1,
Determining a maximum contrast ratio for each frame;
Modulating the output of the laser source such that the output of the laser source has the minimum average power required to provide the determined contrast ratio at a frame rate.   14. The method of claim 13, further comprising selectively modulating an output of the laser light source to change a minimum average power of the output of the laser light source by inputting a control signal to the laser light source in response to an external signal. The method described in.   14. The method according to claim 13, wherein the laser light source is stopped between successive images.